Every short story in this wonderfully varied collection has one thing in common: each features some alteration in history, some divergence from historical reality, which results in a world very different from the one we know today. As well as original stories specially commissioned from bestselling writers such as James Morrow, Stephen Baxter and Ken MacLeod, there are genre classics such as Kim Stanley Robinson's story of how World War II atomic bomber the Enola Gay, having crashed on a training flight, is replaced by the Lucky Strike with profoundly different consequences.